Authorities believe an estimated 7,000-ton meteor that created a panic in Chelyabinsk, Russia, crashed into nearby Chebarkul Lake and produced this circular hole.

Photo: Associated Press

Authorities believe an estimated 7,000-ton meteor that created a...

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TOPSHOTS A view of the wall of a local zinc plant which was damaged by a shockwave from a meteor in the Urals city of Chelyabinsk, on February 15, 2013. A meteor strike in central Russia that left today hundreds of people injured is the biggest known human toll from a space rock, a British expert said. AFP PHOTO / 74.RU/ OLEG KARGOPOLOV--BEST QUALITY FROM SOURCE--OLEG KARGOPOLOV/AFP/Getty Images

With a blinding flash and a booming shock wave, a meteor blazed across the western Siberian sky Friday and exploded with the force of 20 atomic bombs, injuring more than 1,000 people as it blasted out windows and spread panic in a city of 1 million.

While NASA estimated the meteor was only about the size of a bus and weighed an estimated 7,000 tons, the fireball it produced was dramatic. Video shot by startled residents of the city of Chelyabinsk showed its streaming contrails as it arced toward the horizon just after sunrise, looking like something from a science fiction movie about the end of the world.

The largest recorded meteor strike in more than a century entered the Earth's atmosphere about 9:20 a.m. local time at a hypersonic speed of at least 33,000 mph and shattered into pieces about 18 to 32 miles high, the Russian Academy of Sciences said. NASA estimated its speed at about 40,000 mph and said it exploded about 12 to 15 miles high, released 300 to 500 kilotons of energy and left a trail 300 miles long.

"There was panic. People had no idea what was happening," said Sergey Hametov of Chelyabinsk, about 930 miles east of Moscow in the Ural Mountains.

"We saw a big burst of light, then went outside to see what it was, and we heard a really loud, thundering sound," he said by telephone.

The shock wave blew in an estimated 1 million square feet of glass, according to city officials, who said 3,000 buildings in Chelyabinsk were damaged. At a zinc factory, part of the roof collapsed.

The Interior Ministry said about 1,100 people sought medical care after the shock wave and 48 were hospitalized. Most of the injuries were caused by flying glass, officials said.

What is a meteor?

Q: What's the difference between a meteor and a meteorite?

A: Meteors are pieces of space rock, usually from larger comets or asteroids, which enter the Earth's atmosphere. Many are burned up by friction and the heat of the atmosphere, but those that survive and strike the Earth are called meteorites. They often hit the ground at tremendous speed - up to 18,650 mph - releasing a huge amount of energy.

Q: How often do meteorites hit Earth?

A: Experts say smaller strikes happen five to 10 times a year. Large meteors such as the one in Russia on Friday are rarer, but still occur about every five years. Most of them fall over uninhabited areas where they don't injure humans.